1. Field of the Invention
The invention relates to a stand-off cell for an ultrasonic scanner head which stand-off cell is mounted so that is can be disconnected, on the scanner head by a clutch facing and is in contact with the patient through a contact surface and which furthermore has a number of free surfaces.
2. Description of Related Art
In medical diagnostics one is often interested in making a so-called biopsy. I.e. that one by means of a needle takes a sample from the patient. The placing of the needle is often critical, wherefore one is interested in being able to determine this exactly. This applies for example when taking samples of the amniotic fluid.
The supervision of the placing of the needle has been tried by means of ultrasonic scanning where emitted ultrasonic impulses are reflected from the needle and its surroundings and are used for making pictures i.e. by means of a micro computer and a cathode ray tube.
Ordinary scanner heads consist of a row of transducer elements placed in line. As an example one can mention the scanner head which is described in U.S. Pat. No. 4,346,717. Such scanner heads have the drawback, when used for biopsy that one cannot supervise the first 20-50 mm of the area into which the needle is introduced. This is due to the fact that the needle first has to be led diagonally in under the scanner head before it gets into its supervision area.
In order to avoid this drawback it is known from for example German Patent Specification No. 2.906.474 to use special biopsy heads. They consist of an ordinary linear scanner head through which a canal for introducing the needle has been made. However, in order to make room for this canal one has to remove a number of transducer elements in the center of the head. This creates an area that the scanner head is unable to supervise and this will often be inconvenient when introducing the needle. These special biopsy heads furthermore have the drawback that they are very expensive. They cost even more than a normal scanner head.
If one wishes to supervise an area ultrasonically, which area lies close to the surface of the body, it is furthermore known from for example British Patent Application No. 2.009.563 to use a spacer unit between the scanner itself and the body.